High-performance electrocatalysts for oxygen reduction reaction (ORR) are vital to many chemical and energy transformation processes. To date, however, the role of atomic defects in nanocarbon (NC) supports for ORR electro-catalysts is still poorly understood. In this presentation, we report our findings in understanding the contribution of atomic defects in NC supports to a series of transition metals (TM) based electro-catalysts to enhance the ORR activity and stability in an alkaline medium. The defect structures and their local coordination are characterized using Operando X-ray absorption spectroscopy and ex-situ Raman spectroscopy. Moreover, the atomic level structure and morphology of the materials are revealed using high-resolution transmission electron microscopy. Further, density functional theory calculations are used to gain deeper insight into the mechanisms of electro-catalytic processes. Our studies not only result in a highly promising ORR electro-catalyst in an alkaline medium but also open a new avenue for rational design of more efficient catalysts for other chemical and energy transformation processes.